Response of bacterial community structure to disappearance of phenanthrene and pyrene from sediment with different submerged macrophytes

Disappearance of phenanthrene and pyrene (on the basis of butanol-extractable fraction) from sediment with different submerged macrophytes, Hydrilla verticillata (H), Myriophyllum verticillatum (M), Vallisneria spiralis (V) and Potamogeton crispus L. (P), was investigated. A relationship between the remedial effect and the bacterial community structure was analyzed using PCR-DGGE. During a 54-day experimental period, removal efficiencies of the two contaminants were the highest in V treatment, followed by M treatment, H and P treatments, and then unplanted treatment. Moreover, only a small part of the removal increments was caused by plant accumulation, indicating that the enhanced removal was mainly due to microbial degradation. DGGE profile analysis indicated that bacterial community in sediments was relatively stable after planting. PAH-degrading bacteria were widely distributed in all of the sediment samples but species differences among the samples were obvious. Moreover, the DGGE band-based similarity between V. spiralis and the other three plants was the highest in M treatment, followed by H treatment, and then P treatment, which is similar to the trend of removal efficiencies of the two contaminants. Therefore, it can be concluded that the difference between the four submerged macrophytes in the removal of phenanthrene and pyrene from sediment might be largely due to the changes in the microbial community structure.